Electric selection controlling



Alml 8 1947- G. DEAKIN ETAL ELECTRICA SELECTION CONTROLLING CIRCUIT Original Filed May 6, 1945 2 Sheets-Sheerl l ATfToRNEY NVENTORS GERALD DEAKIN HENRY E HERBIG April 8, 1947. Q DEAKm'ETAL Re. 22,861'

ELECTRIC SELECTION kGONTROLLING' CIRCUIT 2 Sheets-Sheet 2 original Filed May 6, 194s INVENToRs. GERALD DEKN HENRY E HERBIG Arm/may Ressuecl Apr. 8, 1947 UNITED STATES PATENT l OFFICE ELECTRIC SELECTION CONTROLLING CIRCUIT Gerald Deakin. New York, N. Y., and Fenry F.

Herbig, Madison, N. J., assgnors to International Standard Electric Corporation, New

York, N. Y., a corporation of Delaware 21 Claims. 1

This invention relates to new and useful improvements in selection controlling circuits and more particularly to circuits for controlling the numerical selecting operation of selector switches employed in automatic telephone exchange systems.

The present invention is an improvement on the control circuits disclosed in the co-pending application of Gerald Deakin, Serial No. 484,184, illed April 23, 1943, now Patent No. 2,380,950, dated August 7, 1945, and the various applications and patents referred to therein.

The invention will be explained with reference to Figs. l and 2 of the drawings which diagrammatically illustrate two modifications of as much of a control system as is necessary for a clear understanding of the various features of the present invention.

In an automatic telephone system calling and called subscribers stations I and 2 (Fig. 1) may be interconnected by means including a plurality of selector switches such as 3 and 4. The numerical operations of the selectors are controlled by the calling subscribers customary impulse sender or other number indicating device through the agency of a register provided at the central exchange. The calling station l is connected to the brushes of selector 3 by non-numerical switches (not shown) and a connecting circuit 6, and the register is attached to the connecting circuit 6 through switching means 5.

The selector Switches are of the customary type having a bank of terminals with which a set of brushes cooperates. In the drawings three brushes are shown for selector 3, although it may have a larger number of brushes. The selector brushes are moved over the terminals while a magnet P is energized and are stopped on a set of terminals when this magnet becomes de-energlzed.

The register comprises a series of switches successively operable by the calling device in accordance with the successive digits of the called number which are dialed by the calling subscriber. A brush and a set of terminals of one of these register switches is shown in Fig. 1. This is the register switch which responds to the digit destined for selector 3. When brush RB is advanced towards one of its ten terminals in accordance with the operation of the calling device ,and closes an energizing circuit for the power magnet P in parallel with its Winding. The selector will start hunting for a terminal which has the same potential applied to it as that applied to the terminal on which the register brush RB is resting.

Before the rela-y AR becomes energized the ground at the armature was connected over resistances R6 and R5 in a network B of the Wheatstone bridge type which is provided in the register, and in multiple through the resistance RI and rectifier S4, to brush RB and thence to negative battery and ground. This makes the left corner of the bridge B negative with respect to the right corner and consequently the grid of a tube Vl negative with respect to the cathode of this tube which is connected to the right corner of the bridge. This is the case when the brush RB is resting on one of the rst five terminals .which are connected to the negative pole of the battery. When the register brush is resting on the second group of ve terminals o the register switch it will connect the positive pole of the battery through resistance R5, resistance R6, and in multiple through resistance Rl and rectifier S2, to ground over the hack contact of relay AR. In this case also the left-hand corner of the bridge will be negative with respect to the right-hand corner.

As the brushes of selector 3 advance and the test brush T makes contact with the successive terminals, current iows from the register brush RB to the selector brush T or Vice Versa, depending upon the relative polarity of the register and selector terminals. However, the left-hand corner o f bridge B and, therefore, the grid o-f Vl will always remain appreciably negative with respect to the right-hand corner of the bridge and cathode of VI until the same potential is applied to both brushes.

When the relay RSR became energized, high tension battery HTB was connected over its lefthand armature and front contact and a resistance vthen over the resistance R4.

R2 to the anodel of vacuum tube VI. Through a condenser CI the high tension battery-is connected with the grid of a second vacuum tube V2, but this grid is maintained negative by a battery connection over resistance R3.

When the brush T of the selector reaches a terminal having the saire potential and polarity as the terminal on which RB is resting, then approximately the same potential will be applied to the cathode and the grid of tube Vl. The characteristic of Vl is such that it triggers off and closes the anode circuit under these conditions. When this happens, then the potential onthe condenser CI will drop sufciently to cause the grid of the second tube V2 to become positive or nearly so, whereupon V2 also triggers off and operates the high speed relay VR. This relay opens the selector magnet circuit and the selector stops.

The anode circuit of tube VI may be traced from the high tension battery HTB, the front contact of RSR, the resistance R2, the anode of VI, the cathode of Vl, the positive corner of the rectifier bridge, resistances R5 and R6 in multiple and then over the brushes RB and T, respectively, to grounded positive or negative battery.v A small amount of current passes through RI and thence in multiple thro-ugh rectiers S2 and S4 to the two'brushes RB and T. However, since RI is shunted by R5 and R6, in-

fsuflclent current will flow over this path to make the control grid of Vl sufliciently negative to stop emission in case high vacuum tubes are used, Preferably gas filled tubes are used in this circuit, because once such tubes are triggered -into action the return of the grid to negative Apotential does not stop or even decrease emission and the relay VR is thus always assured of ample current for operation.

The resistors RI to R6 are of fairly high resistance and not enough current will flow over the test wire during hunting to produce cross- -talk.

When the high tension battery is connected over the front contact of relay RSR the bridge circuit must be kept continuously closed so thatr the left-hand corner of the bridge may be al- -ways negative with respect to the right-hand `the selector side of the bridge by applying ground rst over the back contact of the AR relay and The path to the bridge will never'be opened when the brush T passes from one terminal to the next. As ex'- plained in the above-mentioned application of 'Gerald Deakin, the selector brushes are usually Snot permissible because the test terminals are -multipled and a false test would occur if the- `brush made contact with one terminal while still in engagement with the receiving terminal.

The grounding of the test wire over resistance R4 compensates for'that.

The cathode of vacuum tube Vl must always -be free from ground. This may be accomplished by using floating or indirectly heated cathodes or, as shown, by heating the filament cathodes `of each tube over a small individual transformer T, The primary circuits of each tube trans- 4 former T are connected with a 60 cycle power supply over the front contacts of a relay SR which operates when the register is selected for connection with .circuit 6. This will eliminate all delay in the heating up of the filament. The filaments may be heated from a D. C. source by inserting rectiers in the secondary circuits of the individual transformers T or by providing individual batteries. Such method of heating filaments may be found expedient in small installations where A. C. power is not available.

It will be noted that when the selector and register brushes are resting on the highest negative potential, in the present case 20 volts, then the effective potential of the high tension HTB is augmented. On the other hand, when the brushes are resting on the highest positive potential, then the effective potential of HTB is decreased. Obviously, the potential of HTB must compensate for this drop.

In the arrangement disclosed in Fig. 2, two pairs of rectifers, SI, S2 and S3, S4 are used. Each pair is oppositely polarized andthe rectier pairs provide alternate parallelA paths between the register brush RB and the selector brush T. The grid of a triode VI is connected with one path between the two rectiflers and the cathode with the other path, also between the two rectifiers. The rectr'fiers are so poled that when any current flows from one brush to the other, the grid of tube VI will be always .negative and the cathode of this tube always positive. Only when the brushes RB and T have the same polarity and are at the same potential will the cathode and grid of tube VI attain the same potential and cause the operation of the second vacuum tube V2. In all other respects the circuits of Figs. 1 and 2 are identical.

Since rectifiers have very high resistance to currents flowing in one direction, the only appreciable current that flows during hunting is through high resistance R4 to ground. This will guard against cross-talk. Should the flow of current over the test wire to R4 be found objectionable, this may be completely eliminated by'connecting the resistance R4 to the brush T not at the register but at the selector. This is indicated in dotted lines.

While in Fig. 1 the terminals are shown as separated by four volt steps the circuit of Fig. 1 as well as Fig. 2 will operate on two volt steps or, of course, on larger steps than four volts.

If the rectifier S4 is shunted by a resistance then the tube VI may be used to operate relay VR directly rather than through the agency of a second tube V2. Such arrangement might be objected to on the ground that appreciable current would flow over such shunting resistance when RB is positive with respect to brush T thus producing objectionable cross-talk.

Since the potential of the grid does notchange with respect to the cathode when Vl emits full current, the two tubes VI and V2 may be of the high vacuum type. However, gas filled triodes are preferred, certainly for tube V2.

l'What is claimed is:

1. In combination, a selector switch having a plurality of first contacts and a second cooperating contact, a magnet for controlling the contacting of the second with any ofthe flrst contacts, a register having a plurality of first contacts and a second contact, means for controlling the engagement between the first and second register contacts, a relay for said register having a :contact for controlling the magnet, a vacuum tube in said register having a cathode, a grid and an anode, a source of potential, connections for applying the same potentials to the first contacts of the register and Selector, there being a predetermined difference between the potentials applied to adjacent first contacts, an energizing circuit for said relay .controlled by said vacuum tube, a circuit connecting the second contacts of the register and selector, and connections from the last-mentioned circuit to the grid and cathode of said tube.

2. In combination, a selector switch having a plurality of first contacts and a second cooperat ing contact, a magnet for controlling the contacting of the second, with any of they iirst ,contacts. a register having a plurality of iirst contacts and a second contact, means for controlling the engagement between the first and 'second register contacts, a relay for said register having a contact for controlling the magnet, a vacuum tube in said register having a cathode, a grid and an anode. a source of potential, connections for applying the same potentials to the first contacts `of the register and selector, there being a predetermined diiierence between the potentials applied to adjacent first contacts, an energizing circuit for said relay controlled by said vacuum tube, a circuit having alternate paths connecting the second contacts of the register and selector, means in said paths restricting current ow to a given direction, a connection from the grid to one path and a connection from the cathode to the other path.

3. In combination, a selector switch having a plurality o-f iirst contacts and a 'second cooperating contact, a magnet for controlling the contactingr of the second with any of the iirst contacts, a register having a plurality of first contacts and a second contact, means for controlling the `engagement between the iirst and second register contacts, a relay for said register having a contact for controlling the magnet, a vacuum .tube in said register having a cathode, a grid and an anode, a source of D. C. potential, connections for applying the same positive potentials from said source to one group of the first contacts of the register and selector and the same negative potentials to a second group of said contacts, there being a predetermined voltage difference between the negative als well as the positive potentials applied to adjacent first contacts, an energizing circuit for said relay controlled over the anode of .said vacuum tube, a circuit having'alternate paths connecting the second contacts of the register and selector, a rectifier at least in one of said paths restricting current 'iow to a given direction, a connection from the grid to one path and a connection from the cathode to the other path.

4. In combination, a selector switch having a plurality of first contacts and a second cooperating contact, a magnet for contro-lling the contacting of the second with any of the first contacts, a register having .a plurality of first contacts and a second contact, means for controlling the en gagement between the rst and second register contacts, a relay for said register having a contact for controlling the magnet, a rst and a second vacuum tube in said register, each having a cathode, a grid and an anode, a source of potential, vconnections for applying the same potentials to the first contacts of the register and selector, there being a predetermined difference. between the potentials applied to adjacent first contacta' an energizing circuit for said relay controlled `over the anode `of the second tube, a circuit con.-

nesting the 'second contacts of the registerl and selector, connections from the last-mentioned circuit to the grid and cathode of the first tube, and a connection from the anode of the rst tube to the grid oi the second tube.

5. In combination, a selector switch having a plurality of iirst contacts and a second cooperating contact, ,a magnet for controlling the contacting of the second with any of the first contacts, a register having a plurality of iirst contacts and a second contact, means for controlling the engagement between the first and second register contacts, a relay for said register having a contact for controlling the magnet, a vacuum tube in said register having a cathode,v a grid and an anode, a source or" D. C. potential, connections for applying the same potentials to the rst contacts of the register and selector, negative to one group and positive to a second gro-up, there being a predetermined v-o-ltage difference between the potentials applied to adjacent contacts, an energizing circuit for said relay controlled by said vacuum tube, a circuit connecting the second contacts of the register and selector, a Wheatstone bridge having its first and second corner connected in said circuit, and the third and fourth corner, respectively with the grid and cathode of said tube, resistances in two branches and rectiiiers in the other two branches of said bridge.

6. In combination, a selector switch having a plurality of first contacts and a second cooperating contact, a magnet for controlling the contacting of the second with any of the first contacts, a register having a plurality of rst contacts and a second contact, means forcontrolling the engagement between the rst and second register contacts, a relay forsaid register having a contact for controlling the magnet, a vacuum tube in said register having a cathode, a grid and an anode, a source of D. C. potential, connections for applying the same potentials to the rst contacts of the register and selector, negative to one group and positive to a second group. there being a predetermined voltage difference between the potentials applied to adjacent contacts, an energizing circuit for said relay controlled by said vacuum tube, a circuit having parallel paths connecting the second contacts of the register and selector, two oppositely poled rectifiers in each path, a connection from the grid to one path between the two rectifiers, and a connection from the cathode to the other path between the two rectiers provided therein.

7. In combination, a selector switch having a plurality of terminals and a set of brushes cooperating therewith, a magnet for controlling operation oi' said brushes, a register comprising a switch having a plurality o terminals and a brush adapted successively to engage them, means for operating the register brush to engage any terminal, a relay for said register having a contact for controlling the magnet, tw-o vacuum tubes in said register each having a cathode, va grid and an anode, a connection from the register brush to the selector brush including a rst path in which current is allowed to iiow in one direction only and a second path in which current is allowed to flow only in the opposite direction, a connection from the rst path to the grid of theilrst tube, a connection from the second path to the cathode of the nrst tube, a source of potential, connections for applying the same potentials tothe terminals of the register and of the selector, there being a predetermined rdiierence between the potentials applied to adjacent terminals, an energizing circuit for said relay including the anode of the second tube, and a connection from the grid of the second tube to the anode of the first tube.

8. In combination, a selector switch having a plurality of terminals and a set of brushes co-V operating therewith, a magnet for controlling operation of said brushes, a register comprising a. switch having a plurality of terminals and a brush adapted successively to engage them, means for operating the register brush to engage any terminal, a relay for said register having a contact for controlling the magnet. two vacuum tubes in said register each having a cathode, a grid and an anode, a Wheatstone bridge having rectii'lers in two branches and resistances in the other two branches, two opposite corners of said bridge being connected, respectively, with the register brush and the selector brush, andthe other two, respectively, with the grid and cathode of the first tube, a source of D.'Y C. potential, connections for applying the same DOtentialS to the terminals of the register and of the selector, negative to one group and positive to a second group of said terminals, there being a predetermined voltage difference between the potentials applied to adjacent terminals, an energizing circuit for said relay including the anode of the second tube, and a connection from the grid of the second tube to the anode of the rst tube.

9. In combination, a, selector switch having a plurality of terminals and a set of brushes cooperating therewith, a magnet for controlling operation of said brushes, a register comprising a switch having a plurality of terminals and a brush adapted successively to engage them, means for operating the register brush to engage any terminal, a relay for said register having a contact for controlling the magnet, two vacuum tubesy in said register each having a cathode, a grid and an anode, a connection from the register brush to the selector brush including two parallel paths, two oppositely poled rectiiiers in series in each path, a connection from the grid of the first tube to the first path between the two rectifiers, a connection from the cathode of the iirst tube to the second path between the two rectiiiers, a source of D. C. potential, connections for applying the same potentials to the terminals of the register and of the selector, negative to one group and positive to a second group of said terminals, there being a predetermined Voltage difference between the potential applied to adjacent terminals, an energizing circuit for said relay including the anode of the second tube, and a connection from the grid of the second tube to the anode ofthe rst tube.

l0. In a switching system a selector switch lhaving a plurality of contacts and a rst Contact wiper, control means for moving said wiper to successively establish contact between said wiper and said contacts, a plurality of sources of different steady direct current potential, means for maintaining on each said contact a predetermined steady direct current potential, a second contact wiper for contacting one of said plurality of contacts, means for selecting the one of said plurality of contacts that is contacted by said second contact wiper, potential comparing means having two terminals, means for connecting one of said last mentioned terminals to said first Wiper and the other to said second wiper and for maintaining the same relative polarity between said terminals irrespective of whether the potential on said selected contact is greater or less than the potential of said first wiper, and means under the control of said comparing means for actuating Said control means to arrest said first` wiper when said potential on said selected contact and the potential derived over said iirst wiper are of the same polarity and substantially the same magnitude.

11. A switching system according to claimy 10 in which said potential comparing means comprises an electron discharge tube and in which said means for connecting saidpotentials thereto .comprises a rectier bridge, connections from one pair of opposite diagonal points to two electrodes of said tube respectively, and connections from the other pair of opposite diagonal points to said rst and second wipers.

12. In a switching system, a plurality of conductors, means for maintaining on each 'conductor a predetermined potential, a rectifier bridge circuit, potential comparing means including a high impedance path, means for con'- necting said high impedance path to said rectifier bridge circuit, a iirst connecting means for connecting a, iirst conductor with a point on said bridge circuit, a second connecting means for connecting a second one of said conductors with another point on said bridge circuit, and means including said `high impedance path and response to the connection with the bridge of two conductors whose potentials bear a predetermined relationship to one another for .controlling said second connecting means.

13. The system according to claim 12, and in which said high impedance path comprises a discharge path within a multi-electrode electron discharge tube, two of whose electrodes are connected to diagonally opposite points of said bridge circuit.

14. The system according to claim 12, and in which said high impedance path comprises a discharge path within a multi-electrode electron discharge tube, two of whose electrodes are connected to diagonally opposite points of said bridge circuit and a third electrode is connected with the last-mentioned means for controlling said second connecting means.

15. The system according to claim 12, and in which said bridge circuit comprises a rectier in each of its four branches.

16. The system according to claim 12, and in which said bridge circuit comprises a rectifier in each of two branches and an ohmic resistance in 'each of the other two branches.

17. The system according to claim 12, and in which said iirst connecting means is connected with one and said second connecting means with an opposite diagonal point of said bridge circuit.

18. In a switching system, a plurality of terminal contacts, a plurality of sources, a different steady direct current potential, means for maintaining on each contact a predetermined potential, potential comparing means comprising a single discharge path in -a multi-electrode electron tube, a first connecting means connecting any one of said sources of potential with said comparing means, a second connecting means for `connecting one of. said contacts with said comparing means, 'and means including said electron discharge path Aand operative when two potentials applied to said comparing means bear a predetermined potential relationship to one another for controlling said second connecting means.

19.-The systemaccording to claim 18, andin which` the two. potentials applied to saidcom- 9 paring means are impressed upon two difierent electrodes of said tube.

20. The system according to claim 18, and in which said predetermined relationship between the potentials is that they are the same.

21. In a switching system, a plurality of conductors, means for maintaining on each said conductor a predetermined potential, potential comparing means including two terminals, a first connecting means for connecting a first one of said 10 conductors with a first one of 'said terminals, a

second connecting means for connecting a second one of said conductors with the other of said terminals, and means including said first and second connecting means and responsive to the predetermined relationship between the potentials en the conductors connected by said rst and second connecting means to said potential comparing means for controlling said second connecting means.

GERALD DE'AKIN.

HENRY F. HERBIG. 

